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Numerous installers, cloud services, VM images and stacks are available at BitNami and TurnKey.

MediaWiki is one by Wikipedia (images at BitNami and TKL).

Coppermine and Gallery are two designed specifically for photos and only photos (images at BitNami and TKL); EC2 and VirtualBox-compatible stacks for installation on 3+ platforms. I think TKL has ISOs for appliances as well.